程序要实现的功能是：键盘设定初值并由数码管显示，

程序开始时先将初值送入PWM控制程序，输出相应占空比的

波形，然后监测ad转换得到的数据与设定值的差异调用PID算法

程序，运用增量型PID进行计算，自动调节PWM占空比，

使输出趋近于设定值-The function of the program to be implemented: the keyboard initialization by digital tube display program starts when the first initial value into the PWM control program, the output corresponding to the duty cycle of the waveform, and then the monitoring ad converted the data setting difference call the PID algorithm using incremental PID calculated automatically adjusts the PWM duty cycle output approaches setpoint! !